Jet pump

ABSTRACT

A jet pump comprises a HP inlet vent, a nozzle connected to the HP inlet vent via a HP fluid conduit and configured to discharge a first fluid flowing through the HP inlet into a nozzle discharge zone, a LP inlet vent, a LP fluid conduit connected to the LP inlet vent and configured to discharge a second fluid flowing through the LP inlet vent into the nozzle discharge zone. A mixing tube is provided downstream of the nozzle discharge zone for mixing the first and second fluids and an outlet vent is located downstream of the mixing tube for discharging a mixture of the first and second fluids from the jet pump. The jet pump includes a spinner mechanism upstream of the nozzle discharge zone for causing spinning rotation of at least one of the first and second fluids about a longitudinal axis of the nozzle. In one embodiment the spinner mechanism includes a LP inlet chamber connected to receive the second fluid from the LP fluid conduit, the LP inlet chamber comprising a fluid passageway that extends circumferentially around the nozzle to cause rotation of the second fluid around the longitudinal axis of the nozzle.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 USC 119 to British application no. GB 1406059.4 filed Apr. 4, 2014, and the disclosure of said British application is hereby incorporated by reference in its entirety.

FIELD

The present invention relates to a jet pump and in particular, but not exclusively, to a jet pump for use in the oil and gas industries.

BACKGROUND

Jet pumps or eductors are passive devices that use energy from a high pressure (HP) fluid source to boost the pressure of a low pressure (LP) fluid. The terms jet pump, eductor, ejector and gas jet compressor are used in various industries and refer to the same general type of device. The HP and LP fluids may each consist of liquids, gases or a mixture of liquids and gases.

FIGS. 1 and 2 show the key features of a typical jet pump. HP fluid from a HP source passes through a HP inlet 4 to a jet pump 6, where it passes through constriction known as a nozzle 8 that increases the velocity of the fluid. In this way part of the potential (pressure) energy of the HP fluid is converted to kinetic energy (high velocity fluid). As a result, the pressure of the fluid in a nozzle discharge zone 10 in front of the nozzle 8 drops significantly.

LP fluid from a LP source passes through a LP inlet 12 and is introduced into the jet pump at the nozzle discharge zone 10, where it is entrained in the flow of fluid emerging from the nozzle 8. The mixture of fluids then passes through a mixing tube 14 where momentum and energy are exchanged between the fluids. The mixture finally passes through an expanding diffuser 16 where the velocity of flow normalises and pressure recovery takes place. The pressure at the outlet 18 of the jet pump will be at an intermediate value between the pressures of the HP and LP fluids and the inlets 4, 12. In some jet pumps the nozzle 8 and the mixing tube/diffuser 14, 16 comprise replaceable components that are mounted within a housing 20. Jet pumps have been used successfully in a variety of applications onshore or near the bottom of oil or gas wells. In such situations the HP fluid may be gas or a high pressure liquid such as oil or water. The LP fluid could be gas, or liquid (oil and/or water), or a mixture of gas and liquid.

In some applications, particularly when the HP fluid is a liquid and the LP fluid is predominantly a gas, complete mixing of the HP and LP fluids may not take place. This can adversely affect the operational efficiency of the jet pump.

SUMMARY

It is an object of the present invention to provide a jet pump that mitigates one or more of the aforesaid disadvantages.

According to one aspect of the present invention there is provided a jet pump including a HP inlet vent, a nozzle connected to the HP inlet vent via a HP fluid conduit and configured to discharge a first fluid flowing through the HP inlet into a nozzle discharge zone, a LP inlet vent, a LP fluid conduit connected to the LP inlet vent and configured to discharge a second fluid flowing through the LP inlet vent into the nozzle discharge zone, a mixing tube downstream of the nozzle discharge zone for mixing the first and second fluids and an outlet vent downstream of the mixing tube for discharging a mixture of the first and second fluids from the jet pump, wherein the jet pump includes a spinner mechanism upstream of the nozzle discharge zone for causing spinning rotation of at least one of the first and second fluids about a longitudinal axis of the nozzle.

We have found that by spinning at least one of the first and second fluids about a longitudinal axis of the nozzle, the mixing of the fluids in the mixing tube can be significantly improved. This applies in all situations, including even a situation where the HP first fluid is a liquid and the LP second fluid is predominantly a gas. Complete mixing of the HP and LP fluids can thus be ensured, thereby significantly improving the operational efficiency of the jet pump.

Advantageously, the spinner mechanism includes a LP inlet chamber connected to receive the second fluid from the LP fluid conduit, the LP inlet chamber comprising a fluid passageway that extends circumferentially around the nozzle to cause rotation of the second fluid around the longitudinal axis of the nozzle.

The LP inlet chamber may include a curved wall that extends at least partly around the nozzle. The LP inlet chamber may be substantially involute in shape, being defined by a curved wall that has a decreasing radius of curvature from its upstream end to its downstream end. Alternatively, the LP inlet chamber may be substantially cylindrical in shape.

Advantageously, the LP inlet chamber has a tangential inlet port connected to the LP inlet vent.

Advantageously, the LP inlet chamber has an annular outlet port configured to discharge the second fluid into the nozzle discharge zone.

Advantageously, the spinner mechanism includes a spinner device located within the HP fluid conduit, which is configured to cause rotation of the first fluid around the longitudinal axis of the nozzle. A spinner device may also be provided within the LP inlet chamber.

The spinner device preferably includes at least one helical blade configured to cause rotation of the first fluid as it flows through the HP fluid conduit.

BRIEF DESCRIPTION OF DRAWINGS

Certain embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

FIG. 1 is a sectional side view of a known jet pump;

FIG. 2 is a sectional isometric view of a known jet pump;

FIG. 3 is a sectional side view of a jet pump assembly according to a first embodiment of the invention;

FIG. 4 is a cross-sectional view on live IV-IV of FIG. 3;

FIG. 5 is a sectional side view of a jet pump assembly according to a second embodiment of the invention;

FIG. 6 is a cross-sectional view on live VI-VI of FIG. 5; and

FIG. 7 is a sectional side-view of a nozzle assembly of a jet pump according to a third embodiment of the invention.

DETAILED DESCRIPTION

FIGS. 3 and 4 show a jet pump according to a first embodiment of the invention. The jet pump includes a HP inlet 104 and an HP fluid conduit comprising an inlet tube 106 having a nozzle 108 at one end. A HP first fluid flowing through the inlet tube 106 is discharged through the nozzle 108 into a low pressure nozzle discharge zone 110 in front of the nozzle 108. The nozzle 108 is constricted to increase the velocity of the fluid as it is discharged from the nozzle 108. In this way the potential (pressure) energy of the HP first fluid is converted to kinetic energy as the fluid emerges from the nozzle 108. This reduces the pressure at the low pressure nozzle discharge zone 110.

A low pressure second fluid from a LP source passes through an LP inlet 112 and is introduced into an involute inlet chamber 114 that encircles the inlet tube 106 and is positioned just upstream of the nozzle 108 and the low pressure nozzle discharge zone 110. The involute chamber 114 is defined by a curved wall 116 of decreasing radius that curves around the nozzle 108. The involute chamber 114 is defined between the curved wall 116 and the circular wall of the inlet tube 106. This chamber 114 has a cross-sectional area that decreases from the inlet end to the outlet end of the chamber.

The LP second fluid flowing through the LP inlet 112 into the involute inlet chamber 114 is guided by the curved wall 116 so that it rotates around the inlet tube 106 as shown in FIG. 4. The speed of the rotating second fluid increases as it flows through the chamber 114 as a result of the decreasing cross-sectional area of the involute inlet chamber 114.

The rotating second fluid exits the involute inlet chamber 114 through an annular gap 117 that surrounds the inlet tube 106. The rotating LP second fluid is then combined in the nozzle discharge zone 110 with the first fluid emerging from the nozzle 108 and the first and second fluids are mixed within the mixing tube 118 downstream of the nozzle 108. The spinning motion of the LP second fluid causes the first and second fluids to mix thoroughly within the mixing tube 118. The mixture of fluids then passes through an expanding diffuser 120 where the velocity of the flow normalises as pressure recovery takes place. Finally, the mixture of fluids exits the jet pump 102 at outlet 122. The pressure of the fluid mixture at the outlet 122 will be at an intermediate value between the pressures of the first and second fluids at the HP and LP inlets 104, 112.

In this embodiment the inlet tube 106 and the mixing tube/diffuser 118, 120 are replaceable components that are mounted within a housing 124. Alternatively, the nozzle 108, the mixing tube 118 and the diffuser 120 may be permanently mounted within or formed integrally with the housing 124.

FIGS. 5 and 6 depict a jet pump according to a second embodiment of the invention. This embodiment is similar to the first embodiment described above, except that the low pressure inlet chamber 124 has a different cross-sectional shape.

The second jet pump shown in FIGS. 5 and 6 includes a HP inlet 104 and an inlet tube 106 that has a nozzle 108 at its downstream end. The nozzle 108 is arranged to discharge a first fluid emerging from the nozzle into a LP nozzle discharge zone 110 downstream of the nozzle. The discharged fluid then flows through a mixing tube 118 and a diffuser 120 towards an outlet vent 122.

In the embodiment of FIGS. 5 and 6 the LP inlet chamber 124 is cylindrical and is defined by a curved wall 126 that encircles the inlet tube 106 upstream of the nozzle 108. The LP inlet 112 is connected tangentially to the LP inlet chamber 124, to feed a LP second fluid tangentially into the LP inlet chamber 124. As a result, the LP second fluid rotates around the nozzle 108 before flowing into the LP nozzle discharge zone 110 downstream of the nozzle 108 through, an annular opening 127. The rotational movement of the LP second fluid aids mixing of the second fluid with the high velocity first fluid emerging from the nozzle 108, thereby improving the operational efficiency of the jet pump.

The two fluids are mixed within the mixing tube 118 and the mixture then flows through the diffuser 120 towards the outlet 122. As before, the mixture of fluids emerging from the outlet 122 will have a pressure that is intermediate between the pressures of the first and second fluids at the HP and LP inlets 104, 112.

Optionally, the HP inlet tube 106 may include a mechanical static spinner device 130 located within the HP inlet tube 106 upstream of the nozzle 108, as shown in FIG. 7. This spinner device 130 may for example take the form of helical blades provided on the inner wall of the HP inlet tube 106, which cause the HP first fluid flowing through the HP inlet tube to rotate about the axis of the tube. The spinning motion of the fluid will be maintained as the fluid emerges from the nozzle 108, thereby enhancing mixing of the first and second fluids in the LP nozzle discharge zone 110 downstream of the nozzle 108 and in the mixing tube 118. This spinner device 130 may be combined with either of the LP inlet chambers 114, 124 of the first and second embodiments described above and shown in FIGS. 3-6 so that both fluid streams are spinning as they enter the mixing tube 118. Alternatively the spinner device 130 may be used on its own with a conventional LP inlet arrangement as depicted in FIGS. 1 and 2, in which case spinning motion will be imparted only to the HP first fluids. 

1. A jet pump including a HP inlet vent, a nozzle connected to the HP inlet vent via a HP fluid conduit and configured to discharge a first fluid flowing through the HP inlet into a nozzle discharge zone, a LP inlet vent, a LP fluid conduit connected to the LP inlet vent and configured to discharge a second fluid flowing through the LP inlet vent into the nozzle discharge zone, a mixing tube downstream of the nozzle discharge zone for mixing the first and second fluids and an outlet vent downstream of the mixing tube for discharging a mixture of the first and second fluids from the jet pump, wherein the jet pump includes a spinner mechanism upstream of the nozzle discharge zone for causing spinning rotation of at least one of the first and second fluids about a longitudinal axis of the nozzle.
 2. A jet pump according to claim 1, wherein the spinner mechanism includes a LP inlet chamber connected to receive the second fluid from the LP fluid conduit, the LP inlet chamber comprising a fluid passageway that extends circumferentially around the nozzle to cause rotation of the second fluid around the longitudinal axis of the nozzle.
 3. A jet pump according to claim 2, wherein the LP inlet chamber includes a curved wall that extends at least partly around the nozzle.
 4. A jet pump according to claim 3, wherein the LP inlet chamber is substantially involute in shape.
 5. A jet pump according to claim 3, wherein the LP inlet chamber is substantially cylindrical in shape.
 6. A jet pump according to claim 2, wherein the LP inlet chamber has a tangential inlet port connected to the LP inlet vent.
 7. A jet pump according to claim 2, wherein the LP inlet chamber comprises an annular outlet port configured to discharge the second fluid into the nozzle discharge zone.
 8. A jet pump according to claim 1, wherein the spinner mechanism includes a static spinner device located within the HP fluid conduit, which is configured to cause rotation of the first fluid around the longitudinal axis of the nozzle.
 9. A jet pump according to claim 8, wherein the static spinner device includes at least one helical blade configured to cause rotation of the first fluid as it flows through the HP fluid conduit.
 10. A jet pump according to claim 3, wherein the LP inlet chamber has a tangential inlet port connected to the LP inlet vent.
 11. A jet pump according to claim 4, wherein the LP inlet chamber has a tangential inlet port connected to the LP inlet vent.
 12. A jet pump according to claim 5, wherein the LP inlet chamber has a tangential inlet port connected to the LP inlet vent.
 13. A jet pump according to claim 3, wherein the LP inlet chamber comprises an annular outlet port configured to discharge the second fluid into the nozzle discharge zone.
 14. A jet pump according to claim 4, wherein the LP inlet chamber comprises an annular outlet port configured to discharge the second fluid into the nozzle discharge zone.
 15. A jet pump according to claim 5, wherein the LP inlet chamber comprises an annular outlet port configured to discharge the second fluid into the nozzle discharge zone.
 16. A jet pump according to claim 6, wherein the LP inlet chamber comprises an annular outlet port configured to discharge the second fluid into the nozzle discharge zone.
 17. A jet pump according to claim 2, wherein the spinner mechanism includes a static spinner device located within the HP fluid conduit, which is configured to cause rotation of the first fluid around the longitudinal axis of the nozzle.
 18. A jet pump according to claim 3, wherein the spinner mechanism includes a static spinner device located within the HP fluid conduit, which is configured to cause rotation of the first fluid around the longitudinal axis of the nozzle.
 19. A jet pump according to claim 4, wherein the spinner mechanism includes a static spinner device located within the HP fluid conduit, which is configured to cause rotation of the first fluid around the longitudinal axis of the nozzle.
 20. A jet pump according to claim 5, wherein the spinner mechanism includes a static spinner device located within the HP fluid conduit, which is configured to cause rotation of the first fluid around the longitudinal axis of the nozzle. 